This International Standard specifies a method for the determination of the sulfur content by oxidative microcoulometry of petroleum light and middle distillates with a final boiling point not higher than 400 °C. It is applicable to materials with sulfur contents in the range of 1 mg/kg to 100 mg/kg. Products with sulfur contents above 100 mg/kg can be analysed after dilution with a suitable sulfur-free solvent. Products with sulfur contents below 1 mg/kg can also be analysed by a modified technique described in Annex A. The precision quoted only applies to measurements in the 1 mg/kg to 100 mg/kg range. Nitrogen interferes with the analysis at concentrations above 0,1 % (m/m), and chlorine interferes at concentrations above 1,0 % (m/m), but these interferences are overcome by the addition of sodium azide to the cell electrolyte. Bromine and organometallic compounds also interfere with the analysis at concentrations above approximately 500 mg/kg. NOTE 1 The microcoulometric method is capable of analysing light liquid hydrocarbons boiling in the range from 26 °C to 274 °C (for example, naphtha and MS samples) that undergo pyrolysis at 900 °C to 1 200 °C. The combustion of high boiling components (for example, diesel) can result in the formation of carbonaceous deposits in the inlet portion of the combustion tube, which need to be removed frequently. NOTE 2 The results obtained using this International Standard on light and light-middle distillates generally approximate to those obtained using ISO 4260. NOTE 3 For the purposes of this International Standard, the term “% (m/m)” is used to represent the mass fraction of a material.